Defroster with auxiliary heater for display cases

ABSTRACT

An auxiliary heating device for use in defrosting the evaporator unit in a refrigeration system such as employed in a low temperature display case, such as those found in supermarkets and other stores in which products are stored in low temperature cases but are displayed in a manner for observation by customers. The auxiliary heater is installed by connecting it into the liquid refrigerant line between the condenser and evaporator thereby eliminating the necessity of installing a separate bypass line from the compressor to the evaporator, such as would be necessary if only hot gas refrigerant from the compressor is bypassed into the evaporator during the defrost cycle. The expansion device is also bypassed so that the hot gas refrigerant may bypass the expansion device directly into the evaporator.

United States Patent 1 Redfern et al.

[ DEFROSTER WITH AUXILIARY HEATER FOR DISPLAY CASES [76] Inventors: Howard W. Redfern, l21 Lookout Dr.; William P. Coleman, 631 Martin St., both of Clarksville, Tenn. 37040 221 Filed: May 4,1973 21 Appl.No.:357,093

[52] US. Cl. 62/197, 62/278 [51] lint. Cl. F25!) 41/00 [58] Fieidl of Search 62/151, 155, 156, 196,

[56] References Cited UNITED STATES PATENTS Attorney, Agent, or Firm-Clarence A. OBrien; Harvey B. Jacobson [57] ABSTRACT An auxiliary heating device for use in defrosting the evaporator unit in a refrigeration system such as employed in a low temperature display case, such as those found in supermarkets and other stores in which products are stored in low temperature cases but are displayed in a manner for observation by customers. The auxiliary heater is installed by connecting it into the liquid refrigerant line between the condenser and evaporator thereby eliminating the necessity of installing a separate bypass line from the compressor to the evaporator, such as would be necessary if only hot gas refrigerant from the compressor is bypassed into the 2,630,685 3/1953 Lewis 62/274 evaporator during the defrost y The expansion 2,713249 7/1955 Schordue 62/155 device is also yp o ha the hot gas refrigerant FOREIGN PATENTS 0R APPLICATIONS may bypass the expansion device directly into the 6V3 0 t0 484,541 9/1953 Italy 62/274 p [a r p 3 Claims, 1 Drawing Figure Heai'er 1 i 4 PMENIEU 853?: 3,839,879

Compressor BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to defrost devices and, more particularly, an auxiliary heater that is incorporated into the liquid flow line on the downstream side of the condenser to bypass the refrigerant through the heater where it is heated and then back into the flow line and through the evaporator with the expansion device also being bypassed.

2. Description of the Prior Art Various types of defrosting equipment is employed in refrigeration systems and, in some instances, auxiliary heaters are employed to provide an adequate supply of hot gas refrigerant for passage through the evaporator coil to defrost the coil by melting accumulated frost, ice, and the like, therefrom. In prior US. Pat. No. 3,256,708, issued June 21, 1966, there is disclosed an auxiliary heater device which is incorporated into a refrigeration system in a manner that the hot gas defrost line is provided with the auxiliary heater. This type of installation requires that the hot gas defrost line extend from a position between the compressor and condenser to a position between the expansion device and the evaporator. While such devices are effective and are highly useful in self-contained installations, that is, where the compressor, condenser and evaporator are all contained within the housing or cabinet of the refrigeration unit, in many installations, the compressor and condenser are located at a point remote from the evaporator. For example, the compressor and condenser may be oriented in a machine room, externally of a building, or the like, while the evaporator may be located in a display case or other cooling unit within the interior of the building. Under such circumstances, it is necessary to run an elongated line or tube from the discharge of the compressor to the inlet of the evaporator and, in many instances, multiple evaporators are connected to a common compressor-condenser assembly thus requiring separate lines for each evaporator.

SUMMARY OF THE INVENTION An object of the present invention is to provide an auxiliary heater for use as a defrosting device which can be connected into the liquid flow line of a refrigeration system at a point adjacent to the evaporator or at any point in the liquid flow line between the condenser and expansion device so that the refrigerant may be bypassed through the heater and back into the flow line with the expansion device also being provided with a bypass so that the heated refrigerant may be discharged into the evaporator for melting accumulated frost therefrom, thereby eliminating the necessity of running a tube from the discharge side of the compressor throughout the length of the refrigerant flow line to the evaporator and also eliminating the necessity of using sufficient refrigerant to fill up the additional tubing.

Another object of the invention is to provide a defroster in the form of an auxiliary heater which may be connected into an already existing display case or other cooling unit so that the evaporator may be effectively defrosted without the necessity of running extensive hot gas defrost lines from a compressor oriented externally of a building to each evaporating unit that may be serviced-by the compressor.

Still another importantobject of the invention is to provide an auxiliary heater that may be installed at any point in the liquid flow line of a refrigeration system together with a bypass for the expansion device so that liquid refrigerant maybe bypassed into the auxiliary' heater from the liquid refrigerant flow line with the refrigerant being heated and converted into a gas and dis charged back into the liquid flow line for movement around the expansion device directly into the evaporator for defrosting the evaporator.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS The FIGURE schematically illustrates a refrigeration system with the auxiliary heater forming the defroster incorporated therein.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now specifically to the drawings, a typical refrigeration system is illustrated with the auxiliary heater of the present invention incorporated therein. The refrigeration system includes a compressor 10, a condenser 12, an expansion valve, capillary tube or other expansion device 14, an evaporator 16, all arranged in a manner for circuitous flow. The condenser may be provided with a liquid receiver 18 and the suction line 20 may be provided with a low pressure side accumulator 22. Also, the liquid line from the condenser to the expansion device, as designated by the numeral 24, may have a drier 26 or the like incorporated therein. Also, the refrigeration system may have conventional controls and operates in the usual manner. In supermarkets, stores, and other similar installations, the compressor and condenser are frequently located remote from the evaporator. For example, they may be located on the roof, in a machine room or machine area externally of the building, and multiple evaporators may be employed with a single compressor-condenser assembly. For example, several display cases for frozen foods, display of meat, dairy products and the like may be operatively associated with a single compressor-condenser assembly. In order to defrost the evaporator units, it isnecessary to run a hot gas defrost line from the high pressure side of the compressor to the evaporator so that the condenser and expansion device may be bypassed and the hot gas refrigerant discharged from the compressor directly into the evaporator. This not only requires a long line or tubing but also requires a complicated installation and additional refrigerant. This is especially a problem when installing a hot gas defrost system into existing installations.

In the present invention, a normally open solenoid valve 28 is incorporated in the liquid line 24 at a convenient location at any point between the condenser and expansion valve. On one side of the valve 2S, a conduit 30 is connected and provided with a normally closed solenoid valve 32. On the other side of the normally open valve 28, a conduit 34 is connected and provided with a normally closed valve 36. The conduit 30 enters the auxiliary heater generally designated by the numeral 38 and exits from the other side as conduit 34. The heater device is in the form illustrated in prior US. Pat. No. 3,256,708, the disclosure of which is incorporated herein by reference thereto. The auxiliary heater 38 will effectively heat the refrigerant as it passes there through which will occur during the defrost cycle at which time valve 28 will be automatically closed by the solenoid and the valves 32 and 36 open. Thus, refrigerant will be passed through the heater through conduit 30 and returned back to the refrigerant flow line 24 through conduit 34. The hot gaseous refrigerant discharged by the heater 38 will be bypassed around the expansion device 14 by a bypass line 40 which connects into the refrigerant flow line on both sides of the expansion device. The bypass line 40 is provided with a normally closed solenoid valve 42 therein which will only open during the defrost cycle so that the hot gas refrigerant produced by the auxiliary heater 38 will bypass the expansion device 14 and be discharged directly into the evaporator 16 for defrosting the evaporator. With this installation, the auxiliary heater may be installed at any desired location such as within the cabinet of the display case adjacent to the evaporator. In some instances, the conduit 34 and valve 36 associated therewith and forming a discharge from the auxiliary heater 38 may be connected directly into the flow line on the downstream side of the expansion device 14 but for flexibility of installation, the use of the bypass 40 enables the auxiliary heater to be located in the flow line 24 independent of the particular orientation of the expansion device 14.

With this unit, the condenser is not bypassed as is the case in most hot gas defrost systems and by not bypassing the condenser, the auxiliary heater may be installed at any point in the liquid flow line and this installation also eliminates the necessity of running a separate tube or conduit from the discharge line between the comprcssor and condenser to the evaporator. Rather, this installation permits only a very short section of additional tubing to be used to connect the auxiliary heater to the liquid refrigerant line in a bypass type of connection so that all of the liquid refrigerant passing from the condenser will pass through the auxiliary heater and be heated and converted to hot gaseous refrigerant for discharge into the evaporator without it passing through the expansion device thereby effectively and quickly defrosting the evaporator. This arrangement also permits independent control of the defrost operation for each evaporator in a multiple evaporator system and enables one evaporator of a multiple evaporator system to be defrosted independently of the others thereby enabling flexibility of control of the defrosting operation of a display case depending upon the requirements of each type of display case. In addition, this installation provides a flexibility of orientation so that the auxiliary heater may be easily positioned within the interior of a cabinet and connected to a suitable electrical source for heating the heat exchange liquid in the auxiliary heater which will provide an adequate heat source or reservoir of heat for heating an adequate volume of refrigerant to convert it to a hot gaseous refrigerant for effectively defrosting the evaporator.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. In a refrigeration system including a compressor, a condenser, an expansion device and an evaporator arranged in series relation with the condenser being connected to the expansion device by a liquid refrigerant flow line, that improvement comprising an auxiliary heater connected in bypass relation to the liquid refrigerant flow line, said auxiliary heater being connected into the liquid flow line in bypass relation between the condenser and expansion device and including a normally open valve in the liquid flow line which is closed during the defrost cycle and a normally closed valve connecting the inlet side of the auxiliary heater with the liquid flow line between the condenser and the nor mally open valve in the liquid flow line and a normally closed valve on the discharge side of the heater communicating the discharge side of the heater with the liquid flow line between the normally open valve in the flow line and the expansion device, and bypass means associated with the expansion device for bypassing hot gaseous refrigerant around the expansion device into the evaporator.

2. The structure as defined in claim I wherein said bypass means for the expansion device includes a bypass line having a normally closed valve therein which is open during'the defrost cycle thereby enabling the hot gaseous refrigerant to bypass the expansion device during the defrost cycle.

3. The structure as defined in claim 2 wherein the compressor and condenser are located remotely of the evaporator such as exteriorly of a building when the evaporator is in a display case for food products thereby enabling installation of the auxiliary heater and expansion device bypass adjacent the evaporator with a minimum of additional line incorporated intothe sys- 

1. In a refrigeration system including a compressor, a condenser, an expansion device and an evaporator arranged in series relation with the condenser being connected to the expansion device by a liquid refrigerAnt flow line, that improvement comprising an auxiliary heater connected in bypass relation to the liquid refrigerant flow line, said auxiliary heater being connected into the liquid flow line in bypass relation between the condenser and expansion device and including a normally open valve in the liquid flow line which is closed during the defrost cycle and a normally closed valve connecting the inlet side of the auxiliary heater with the liquid flow line between the condenser and the normally open valve in the liquid flow line and a normally closed valve on the discharge side of the heater communicating the discharge side of the heater with the liquid flow line between the normally open valve in the flow line and the expansion device, and bypass means associated with the expansion device for bypassing hot gaseous refrigerant around the expansion device into the evaporator.
 2. The structure as defined in claim 1 wherein said bypass means for the expansion device includes a bypass line having a normally closed valve therein which is open during the defrost cycle thereby enabling the hot gaseous refrigerant to bypass the expansion device during the defrost cycle.
 3. The structure as defined in claim 2 wherein the compressor and condenser are located remotely of the evaporator such as exteriorly of a building when the evaporator is in a display case for food products thereby enabling installation of the auxiliary heater and expansion device bypass adjacent the evaporator with a minimum of additional line incorporated into the system. 